The present invention relates to a swash plate compressor of the variable stroke volume type which is adapted for use with an air conditioning system for vehicles.
Prior-art variable capacity compressors are set forth in U.S. Pat. Nos. 3,959,983, 3,861,829, Japanese Patent Examined Publication No. 4195/1983, U.S. Pat. No. 4,178,135 and Japanese Patent Examined Publication No. 2390/1986. In general, any of the compressors disclosed in these prior patents includes a rotary swash plate assembly having a rotary portion, the mass size and mass distribution of which are determined to balance the moment produced by the reciprocating motion of pistons, connecting rods and associated components over the whole ranges of inclinations or nutational angles and rotational speeds of the swash plate assembly. Also, in order to maintain the aforesaid balanced state, the rotary swash plate is provided with a ring-shaped balancing weight at one end of the hub of the swash plate or with a balancing weight at the periphery of the same.
In the aforementioned prior art, however, the compressor of the type in which the ring-shaped counterweight is attached to the hub of the rotary swash plate involves a problem in that the length of the compressor is increased in its axial direction. Also, the compressor of the type in which the counterweight is attached to the outer periphery of the hub involves a problem in that the compressor is increased in outer diameter. Accordingly, the prior art encounters various difficulties when the compressor is to be reduced in size and weight, and this may lead to a problem in that, when the compressor is to be incorporated in the engine compartment of a vehicle, the layout is limited.
If the aforesaid counterweight or balancing weight is omitted or reduced in weight in order to reduce the size and weight of the compressor, the moment produced by the reciprocating motion of the pistons or the like does not balance with the moment derived from the mass of a rotary member of the rotary swash plate assembly. This may cause an excessive level of vibration while the main shaft of the compressor is rotated at high speed. In addition, this may lead to an increase in the angular moment acting in the direction in which the length of piston stroke is increased, and hence, an increase in the level of force required for capacity control. This could result in a problem such as a lowering in control characteristics for capacity of the compressor.
Also, in accordance with the prior art, in order to restrict the maximum and minimum inclinations of the rotary swash plate, the length of travel of a pin serving as the nutational center of the rotary swash plate is limited in its axial direction. For this reason, the position of an inclination restricting portion serving to restrict the maximum and minimum inclinations of the swash plate is substantially coincident with or close to the nutational center of the swash plate. As a result, an excessive force acts on the aforesaid inclination restricting portion or pin and this may cause various problems; for example, the inclination restricting portion might undergo deformation or breakage.